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Electrical Engineering
Electrical engineering is a field of engineering that deals with the study and application of electricity, electronics and electromagnetism.
23,056 Questions
What is the purpose of the automatic voltage regulator?
The purpose of an adjustable voltage regulator is to have a regulator that can give out variable voltages. This is in contrast to a fixed voltage regulator which only outputs one voltage, which it is rated for.
To allow for adjustable voltage, usually the resistors on the output of the regulator just need to be swapped for different values to give differing output voltages.
Inverse Definite Minimum Time Lag = IDMT relay
It's a electromagnetic type rotating disk relay.
Tripping time of relay decreases with increasing fault current.
see http://myweb.tiscali.co.uk/robert.booth/uni/docs/Power%20Supply%20Assignment%203.pdf
Why is identification of the vector group of transformer important?
Vector group means it defines the primary & secondary side connection type of the transformer.For example DY says D for the delta connections (windings connected between two phases) & Y for the star connections (windings connected between two phases). That's why identification of the vector group of transformer is important.
AnswerVector groups specify whether two or more three-phase transformers can be paralleled with each other. In order to do so, their angular displacements must be the same. Transformer connections listed in the Vector Group tables, categorise transformer connections in terms of their angular displacements.
Why is an induction motor called rotating transformer?
A motor rotor rotates due to an interaction between magnetic fields of the rotor and stator, where either may use permanent magnets, electromagnets, or a combination of both to effect the interaction.
This interaction is based on the principle of opposite attraction and like repulsion related to magnets.
Either the rotor or stator creates an electromagnetic field, and the opposite component (rotor or stator) tries to attract and repel the appropriate magnetic poles to 'lock' position with the electromagnetic field.
The magnetic field is 'rotated' electrically by applying voltage to different windings within the motor in sequence, and since the moving component always tries to lock position with the magnetic field, the rotor will constantly rotate while trying to align its magnetism.
the relay used to protect the generator/motor from overload currents. And to protect insulation of the stator windings.
How do you check polarity of transformer?
H1 H2, X1 X2 is subtractive polarity--either above 9000Volts or 200 KVa
H1 H2, X2 X1 is additive polarity--both must be below the above values.
These values and determinations, however, are a NEMA standard. Non-standard transformers (foreign) may be different.
Make a temporary connection between H1 and the X1/X2 terminal. Apply a low test voltage to the H1 and H2. Read the voltage across H2 and the X1/X2 terminal.
--If the output voltage is higher than the test voltage then the transformar is additive.
--If the output voltage is lower than the test voltage then the transformer is subtractive.
What is the UK 3 phase voltage?
The nominal voltage in the UK is 400/230 V. That is 400 V line-to-line (i.e. line voltage), and 230-V line-to-neutral (i.e. phase voltage). Allowable variation is +10% and -6%.
What is the importance of a voltmeter to a technician?
When a technician uses a voltmeter he or she can measure the power going through a circuit. It can test the safety and reliability of a an appliance also.
Another Answer
A voltmeter is used to measure the potential difference, or voltage, between conductors. To measure power (as mentioned in the original answer) you need a wattmeter, not a voltmeter.
The purpose of a circuit breaker is to open the circuit in the event of an overload. Wires/conductors are only rated for a specific Amperage. If this amperage is exceeded the conductor/wire begins to heat up and given enough time it becomes a fire hazard.
For instance a 15 amp breaker will trip once the Amps drawn through that circuit exceed 15 amps.
The short answer is to keep you safe.
Which of the following condition exist in a circuit of pure resistance?
in a circuit of pure Resistance (r), IE. voltage source (12 v DC battery) and pure resistance (a light bulb). the voltage (v) and current (i) will be in phase. by adding capacitors and/or inductors to the circuit V and I will be pulled out of phase.
Theory for brake test on three phase induction motor?
why three phase induction motor is delta connected
What is difference between modulator and demodulator?
Modulation is used when information is available in analog form that varies the frequency and/or amplitude of a lower frequency wave, depending on the information it carries. The role of modulation is to place this information onto a carrier frequency that can be transmitted more readily and with least loss of information. There are three fundamental types of modulation - frequency modulation, amplitude modulation and phase modulation. In each of these, a carrier frequency is modulated by a lower frequency, to form a modulated carrier wave. A modulator modulates the carrier frequency, while a demodulator detects the modulation on the carrier wave and recovers the original lower frequency waveform at the destination. For many years the modulated carrier wave was converted to a radio signal. Now it is often an electrical signal which is sent down a teleohone line; the information is usually a set of pulses going between computers. When computers are connected to each other in a two-way conversation, the MOdulator and DEModulator are combined into a single device called a MODEM.
Variable DC power supply is:
Variable - you can adjust it
DC - direct current, electrons (electricity) flows in only one direction
power supply - power supply
Together, it's an adjustable one-way power supply
Hope you find this useful...
What is the physical meaning of power angle in a power system?
a curve drawn for power against load angle
maximum power occurs at load angle of 900
maximum power will be transffered from sending end to receiving end when the reactance is 1.732 times its reactance
The new principal inside welding machines is based on metal-arc welding, whereas the older welding machines used electromagnetic winding to increase the current in welding rods.
Why the output voltage of transformer increases when capacitive loading is used?
if the load is capacitance then reactive power is injected in the circuit, as we know that reactive power is directly proportional to the voltage, if there is increase in reactive power automatically voltage at load end of the tranformer is increases
Explain working of a DC Generator with diagram?
A dc generator is a machine which works on the principle of electro magnetic induction $it converts the mechanical energy into electrical energy.
What are the Advantages and disadvantages of delta and wye transformers?
copper losses Comment: Advantages: Their operation is silent They have a high efficiency They are relatively safe Disadvantages Expensive Copper losses and hysteress losses
Rubies are a nonconducting gem stone. Almost all crystals, stones and gemstones are nonconductors, with a few rare exceptions, such as graphite.
What is the importance of IEE regulations?
I.E.E stands for Institution of Electrical Engineering and a regulation is basically just a certain rule so in this case an I.E.E regulation would be: The employer must provide the correct protective equipment for his/her employees in and electrical engineering working environment
How do you reduce the hysteresis loss?
Hysteresis losses are a function of the magnetic characteristics of the magnetic circuit, so there is very little you can do to minimise hysteresis losses other than to reduce the primary voltage to a transformer if that is at all practicable. These losses are really in the hands of the manufacturers who design and manufacture magnetic circuits.
b'coz transformer is not a moving parts so it works on the princeple of mutual induction
